Isabell Diogo

Analysis of pneumatization and neurovascular structures of the sphenoid sinus using cone-beam tomography (CBT).

Background The sphenoid sinus is a frequent target of paranasal sinus surgery. Because of the high risk of injuring the surrounding structures (e.g. internal carotid artery, optical nerve) a preoperative imaging is absolutely necessary. Purpose To analyze the possibilities of cone-beam computed tomography (CBCT), which is especially quite a new technique in ENT, in the evaluation of the sphenoid sinus, its surrounding structures, and the corresponding anatomical variations. Material and Methods This was a retrospective, single-centre study of 580 patients (1160 sides = cases). The Accu-I-Tomo-F17 was used. Pneumatization of sphenoid sinus, course of internal artery, course of optical nerve, and dehiscence of the bony canals were evaluated. Results In the case of pneumatization a type I (completely missing or minimal sphenoid sinus) was found in two patients (0.3%), type II (posterior wall of sphenoid sinus is in front of the anterior wall of the sella) in 38 patients (6.6%), type III (posterior wall is between anterior and posterior wall of sella) in 332 patients (57,2%), type IVa (posterior wall is behind the posterior wall of sella without air dorsal the sella) in 104 patients (17.9%), and type IVb (similar to type IVa but with air dorsal the sella) in 104 patients (17.9%). In 1025 cases (89.5%) a smooth course of the internal carotid artery was found whereas a free course could be detected in 120 cases (10.5%). Defects of the bony canal of the optical nerve were found in 16.7% and of the internal carotid artery in 2.7% of the cases. The optical nerve showed a free course through the sphenoid in 151 cases (13.7%) and a smooth course in 1007 cases (87.0%). Conclusion CBCT could evaluate all relevant anatomic structures and answer the questions of different anatomical variants. A modified classification of the pneumatization of the sphenoid sinus could be described. Frequencies of anatomical variations are in accordance with the current literature of CT research.

Analysis of the fossa olfactoria using cone beam tomography (CBT)

Abstract Conclusion: A cone beam tomography (CBT) examination of the olfactory area with its different variants allows development of an individual anatomical-radiological risk profile of the ethmoid and the identification of so-called ‘dangerous ethmoids.’ Objective: Preoperative imaging performed with high-resolution CBT is imperative for analysis of the risk of injuring the olfactory fossa during sinus surgery. This study aimed to analyze the relevant parameters. Methods: This was a retrospective, single-center study of 141 patients. The Accu-I-Tomo F17 was used. Keros type, the point of the anterior ethmoid artery, and the angle between the lateral lamella and the cribriform plate (αlc) were evaluated. Results: The Keros types were distributed as follows: type I, 13% (αlc: 131°); type II, 64% (αlc: 116°); type III, 23% (αlc: 108°) (p < 0.001). The angle of the olfactory fossa and the position of the anterior ethmoid artery (free course: αlc=112° vs integrated into the skull base: αlc= 120°) was significantly different. Discussion: Surgical procedures in Keros type III where the height of the lateral lamella is much longer than in type II or type I, with an angle of nearly 107° between the lateral lamella and the cribriform plate, are expected to be safer in comparison with Keros type II with 116° and Keros type I with 131°.

Indications of cone beam CT in head and neck imaging

Abstract Conclusion: Cone Beam Computed Tomography (CBCT) can be widely used in imaging of bony structures of the anterior and lateral skull base. Significant differences of applied dosages result from the different protocols of the various indications. Objectives: CBCT is increasingly being used in head and neck imaging. Until now, no precise knowledge about its dedicated usage existed. Methods: All CBCT of 2012 and 2013 were analysed with regard to the technical parameters, the performance, and the indication for imaging. Results: In total, 1862 patients were examined in 2012 and 2013. The top eight indications of the anterior skull were (1) chronic rhinosinusitis with disturbed nasal breathing (30.3%); (2) chronic rhinosinusitis (17.6%); (3) midfacial traumatology (13.7%); (4) disturbed nasal breathing (12.8%); (5) acute rhinosinusitis (7.9%); (6) polyposis nasi (6.3%); (7) search for focus (3.9%); and (8) persistent rhinorrhea (1.2%). For the lateral skull base, the top eight were (1) control after cochlear implantation (28.4%); (2) cholesteatoma (19.7%); (3) visualization of ear anatomy (8.7%); (4) chronic otitis media mesotympanalis (6.3%); (5) conductive hearing loss (5.1%); (6) suspected mastoiditis (4.8%); (7) pathology of external auditory canal (4.8%); and (8) otosclerosis (3.3%). Applied dosage for the anterior skull base was significantly lower than for the lateral skull base (2.90 mGy vs 5.92 mGy, p < 0.05); 2.4% and 3.6% of patients’ images, respectively, had to be repeated.

Visualisation of the Bonebridge by means of CT and CBCT

BackgroundWith the Bonebridge, a new bone-anchored hearing aid has been available since March 2012. The objective of the study was to analyse the visualisation of the implant itself as well as its impact on the representation of the bony structures of the petrosal bone in CT, MRI and cone beam CT (CBCT).MethodsThe Bonebridge was implanted unilaterally in two completely prepared human heads. The radiological imaging by means of CBCT, 64-slice CT, 1.5-T and 3.0-T MRI was conducted both preoperatively and postoperatively. The images were subsequently evaluated from both the ENT medical and nd radiological perspectives.ResultsAs anticipated, no visualisation of the implant or of the petrosal bones could be realised on MRI because of the interactive technology and the magnet artefact. In contrast, an excellent evaluability of the implant itself as well as of the surrounding neurovascular structures (sinus sigmoideus, skull base, middle ear, inner ear, inner auditory canal) was exhibited in both the CT and in the CBCT.ConclusionThe Bonebridge can be excellently imaged with the radiological imaging technologies of CT and CBCT. In the process, CBCT shows discrete advantages in comparison with CT. No relevant restrictions in image quality in the evaluation of the bony structures of the petrosal bones could be seen.

Differences of radiological artefacts in cochlear implantation in temporal bone and complete head

Abstract Objectives Accurate radiological evaluation of cochlear implants is essential for improvement of devices and techniques and also for assessing the position of the electrodes within the cochlea. Radiological study of implants has focused on isolated temporal bones. Previous studies showed relevant sizes of artefacts (dimensions of the radiological image compared with the actual dimensions of the electrode) in visualization of cochlear implants in computed tomography and cone beam computed tomography (CBCT). In this study, we aimed to obtain CBCT images of cochlear electrodes in isolated temporal bones and in whole heads and to assess the differences in image quality between the two. Methods Cochlear electrodes were implanted in three complete human heads. Radiological examinations were performed using a single CBCT scanner with varying x-ray tube currents, voltages, and rotation angles. The temporal bones were then removed and the same radiological examinations were repeated, with and without the receiver coils. Artefacts from a basal electrode (electrode 9) and an apical electrode (electrode 2) were calculated. These were compared with each other by measuring the diameter of the image of the electrode (electrode inclusive of imaging artefacts) and with the real electrode diameters from the manufacturers data. Additionally, the radiological diameters (inclusive of artefact) of the electrodes were compared to the cross-sectional diameters of the basal and apical coils of the cochlea at the locations of these two electrodes. Results In comparison to the real electrode diameters, radiological artefact proportions of 51–58% for electrode 9 and 56–61% for electrode 2 were calculated. The differences between whole head images (group 1) and temporal bone images with and without the receiver coil (groups 2 and 3) were highly significant for each protocol (P < 0.001). Discussion and conclusion These results indicate that it is not possible reliably to determine the exact intracochlear positions of electrodes using CBCT. Imaging of isolated temporal bones produced significantly greater artefacts than imaging of the whole head. Evaluations of image quality based only on results for isolated temporal bones are not transferable to clinical situations, and should be assessed critically.

Prospective evaluation of reliability of cone‐beam computed tomography in detecting different position of vibroplasty middle ear implants

This study had the following objectives: (i) to determine the accuracy of determination of Vibrant Soundbridge position in the spectrum of typically implanted sites in the middle ear, (ii) to assess interobserver agreement between three observers with different levels of radiology experience and (iii) to determine the suitability of cone‐beam computed tomography (CT) to be used as the baseline radiological assessment post implantation, confirm ferromagnetic transducer (FMT) position.

Reduction of Radiation Dosage in Visualization of Paranasal Sinuses in Daily Routine

Background. Preoperative imaging of the nose and paranasal sinus is standard in otorhinolaryngology. Previous studies on phantoms demonstrated the potential for dose reduction of cone beam computed tomography (CBCT) by varying the application parameters. Methodology. Based on previous studies, the standard protocol of paranasal sinus imaging by CBCT was altered. One hundred and fifty examinations using the old protocol (01/2010–01/2011, high dosage) and 150 examinations using the new protocol (09/2012–09/2013, low dosage) were evaluated and compared for the visibility of 17 anatomical structures, the Lund-Mackay Score, and technical parameters. Results. Alteration of the protocol resulted in a significant reduction in dosage (6.64 mGy versus 2.88 mGy). Both groups showed the same amount of pathology (Lund-Mackay Score: 4.95 ± 3.79 versus 5.26 ± 5.77; p = 0.558). There was a significant better visibility of the anatomical structures (all visible = 1, nothing visible = 4) (results: 1.25 versus 1.17; p = 0.001) in the low-dosage group. Conclusion. Despite a significant reduction in the applied dosage, reliable visualization of the bony anatomy of the anterior skull base is possible by CBCT. This demonstrates the need for the discussion of the required clinical imaging quality.

Reply to ‘Right statistical methods should be driven to get the right answers from research studies’

We thank the commentators for their criticism and their additional information and interpretation, but some misinterpretation by the commentators have to be commented on. Their main criticism is regarding the statistical methods used in our article, especially concerning statistics in Material and Methods. Correlation of pneumatization and courses of the structures, we did of course perform the chi-square test with Cramer’s V-test (because of frequencies ,5%) and bivariate test. We regret this possible misunderstanding term, but results and significances of the paper are completely correct. To repeat the results, the correlations between pneumatization and courses of the internal carotid artery and optical nerve as well as the correlation between the artery and optical nerve itself were all highly significant (P , 0.001; Cramer’s V between 0.199 and 0.370; Person chi-square between 16.253 and 156.839). In agreement with the reviewers we did not include this information in the paper because focus of this study was not to demonstrate statistical correlations. The main aim was to demonstrate that cone beam computed tomography (CBCT) can visualize the sphenoid sinus as good as conventional CT or anatomical studies and to demonstrate frequencies of anatomical variants. One comment can only be a mistake. The commentators write: “The present study is one of them presenting no correlation between the degree of sphenoid sinus aeration and the free course of the carotid artery and the optic canal’. This is simply not correct. We describe the different frequencies of free courses in dependence of the pneumatization (Table 3). We have just not included the statistical results of the chi-square-test. Of course these are statistical significant (optical nerve: chi-square-value 1⁄4 44.452, P , 0.001; Cramer’s V-value1⁄4 0.196, P , 0.001; carotid artery: chi-square value 1⁄4 156.839, P , 0.001; Cramer’s V-value 1⁄4 0.370, P , 0.001). Regarding our mistake of spelling “internal sphenoid artery”, we regret this and meant of course the internal carotid artery. Additionally, we found right now one more mistake of spelling. In the Material and Methods we defined the dehiscence by a bony gap of 0.3 mm and in the Discussion we defined 1.00 mm. Our intention was to define the dehiscence by a bony gap of 1.00 mm. We regret this erroneous data. In conclusion, we can all experience that questions arise due to lack of information. On the other hand, it is impossible to include all information every time in one paper. From our point of view, with the current additional information, no really criticism remains because the correct statistical tests were performed but just not described. Again, we regret the missing information in the Material and Methods section and want to point out the importance of knowing the individual anatomy prior to sphenoid sinus surgery. Our paper demonstrates a relevant number of patients and frequencies of anatomical variants. It points out the possibilities of cone beam CT as a reliable diagnostic device.